A campaign was launched this morning to fight the plan for Kingsway which opponents say will cause a fresh logjam in the town centre just 18 months after the opening of its long-awaited relief road.
County Hall bosses want to make the road inaccessible for vehicles from Liverpool Road as part of a new scheme for a "super cycleway" into Preston.
Locals have reacted with anger, claiming the detour for traffic coming up Penwortham Hill will funnel drivers into the already busy junction with Cop Lane and Priory Lane.
And with the main A59 being reduced at that point to just one lane in each direction since roadworks were completed near to the new Tesco store, residents are worried their town will see a return to the traffic problems the bypass was meant to solve.
Local councillors and the Vicar of St Mary's Church, which is accessed from Kingsway, attended a drop-in meeting with residents at The Venue - the town's former library.
"We won't be able to get a hearse down there, or wedding cars, if this goes ahead," said Rev Chris Nelson.
"It seems odd that they are closing off one of the widest roads in Penwortham and diverting traffic into the middle of the town and down a narrow road."
Coun David Howarth, who represents Penwortham on county, district and town councils, addressed the meeting and added: "This is the main access road to more than 1,000 houses and a health centre.
"It is the route of the 119 circular bus which a lot of elderly and disabled people depend on.
"All the traffic will now have to go to the crossroads at the top and turn right down Priory Lane which will be single lane because of cars parked on one side.
"It is just absolute madness."
Today's drop-in meeting was attended by dozens of residents who are opposed to the one-way scheme.
One said: "They are just going to push all that traffic up the road to the junction with Priory Lane and Cop Lane. It's going to be very dangerous, as well as a bottleneck."
Another warned: "That whole junction, which has just been redesigned, is going to fail because it is single lanes and it isn't geared up for right turns.
"I will have three sets of traffic lights, a roundabout and a 0.7-mile detour to get where I want to be. The boss of LCC Highways needs to come here and explain this to us."
Opponents only have until July 30 to lodge objections to the plan in writing.
Rev Nelson said: "We have two signs on Penwortham Hill directing drivers to St Mary's Church, one coming up and one going down. If it becomes 'no entry' then they will become redundant.
"I'm all for a cycle highway, I like it as a cyclist. But the problem is most cyclists aren't using it for some reason.
"On Sunday we had the Manchester to Blackpool cycle ride through here and I was watching as all the riders came down Penwortham Hill and not one of them used the cycle lane.
"This whole thing needs rethinking to solve the problem that is there and not the problem that isn't. Let's not throw the baby out with the bath water."